McKnight Thomas D, Riha Karel, Shippen Dorothy E
Department of Biology, 3258 TAMU, Texas A&M University, College Station 77843, USA.
Plant Mol Biol. 2002 Mar;48(4):331-7. doi: 10.1023/a:1014091032750.
Telomeres, the complex nucleoprotein structures at the ends of linear eukaryotic chromosomes, along with telomerase, the enzyme that synthesizes telomeric DNA, are required to maintain a stable genome. Together, the enzyme and substrate perform this essential service by protecting chromosomes from exonucleolytic degradation and end-to-end fusions and by compensating for the inability of conventional DNA replication machinery to completely duplicate the ends of linear chromosomes. Telomeres are also important for chromosome organization within the nucleus, especially during mitosis and meiosis. The contributions of telomeres and telomerases to plant genome stability have been confirmed by analysis of Arabidopsis mutants that lack telomerase activity. These mutants have unstable genomes, but manage to survive up to ten generations with increasingly shortened telomeres and cytogenetic abnormalities. Comparisons between telomerase-deficient Arabidopsis and telomerase-deficient mice reveal distinct differences in the consequences of massive genome damage, probably reflecting the greater developmental and genomic plasticity of plants.
端粒是线性真核染色体末端的复杂核蛋白结构，与合成端粒DNA的酶——端粒酶一起，对于维持基因组的稳定是必需的。该酶和底物共同发挥这一重要作用，通过保护染色体免于核酸外切酶降解和端对端融合，并补偿传统DNA复制机制无法完全复制线性染色体末端的缺陷。端粒对于细胞核内的染色体组织也很重要，尤其是在有丝分裂和减数分裂期间。通过对缺乏端粒酶活性的拟南芥突变体的分析，已经证实了端粒和端粒酶对植物基因组稳定性的贡献。这些突变体具有不稳定的基因组，但通过端粒日益缩短和细胞遗传学异常，设法存活了多达十代。端粒酶缺陷型拟南芥和端粒酶缺陷型小鼠之间的比较揭示了大规模基因组损伤后果的明显差异，这可能反映了植物更大的发育和基因组可塑性。
